fix(fs): Handle Snap mount lookup failures in ensureDir

[leumor]

Summary

• remove the Files.getFileStore(path) probe from Dirs.ensureDir, which can throw Mount point not found under Snap mount namespaces
• set POSIX permissions directly via Files.setPosixFilePermissions and keep permission failures non-fatal
• treat unsupported POSIX attributes as a debug-level skip
• add tests covering IOException and UnsupportedOperationException during permission setting

How to test

• run ./gradlew test --tests *DirsTest
• run the node in an Ubuntu Snap container and verify startup no longer logs the Mount point not found warning from network.crypta.fs.Dirs

Notes

• base branch for this PR is release/2 (requested current branch)
• behavior remains best-effort for filesystem permissions and startup is unchanged aside from eliminating the FileStore lookup failure path

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud